Building new gaming rig

Hey, im gonna build a new gaming PC over this summer, and I figured why not come to the Techspot forums to ask for Advice, Help or anything else. So here's what I got, and what I plan on sticking with so far.

•Case: Cooler-Master Haf X: Ultimate Full Size Gaming Chassis(Big, for air circulation, and no space issues.)

•Graphics: XFX ATI Radeon HD6870 1 GB DDR5 2DVI/HDMI/2x Mini DisplayPort PCI-Express Video Card HD687AZNFC(I plan on crossfiring two of these, do I need a long crossfire bridge connector or a short one? Also is this a bad idea with these cards or good?)

•PSU: Last but not least, Corsair CMPSU-850TX 850-Watt TX Series 80 Plus Certified Power Supply compatible with Intel Core i7 and Core i5(I figured this was a good choice from reviews I read and its a reasonable price. Or would this be too little power?)

Thats about it. This is NOT including fans obviously, and im not going with liquid cooling, also how many extra fans should I get? Im also not getting a soundcard.
I dont really have any more questions. So thanks for any help you can give!

The CPU you have selected is Sandy Bridge i5 Core series, which is LGA1155, whereas the motherboard is for the previous generation LGA1156 socket.

The above two items will NOT work together.

I'd change your hard disk to a Samsung SpinPoint F3 1TB hard disk as its about the fastest 7,200rpm disk currently and highly recommended.

Stick to one type of RAM, just buy two packs of the same thing - Make sure the Motherboard QVL (qualified venders list) has them listed as tested with the motherboard before ordering.

I recommend different to the TX850 PSU, get a HX750 or HX850 Corsair unit instead. Its much better built, and has 2 years more warranty. The Corsair TX series is not as good as it once was, and I strongly recommend against it.

750w is enough to power your propsed system with 2 of those graphics cards installed. 620w is more than enough if you never plan to add a second graphics card.